Define eutrophication. What is ill effect of eutrophication?

Eutrophication is a phenomenon that occurs in water bodies. Fertilizers run of from crop fields lead to accumulation of the chemicals in water bodies which results in algal blooms. These alagal blooms thus block the sunlight from penetrating into the aquatic bodies. The aquatic plants thus do not get sunlight to synthesize food and oxygen, thus causing Eutrophication.

Eutrophication causes toxicity in water bodies and makes the water polluted. Also, since the oxygen content decreases, the biological oxygen demand increases. Less content of oxygen effects life forms and aquatic organisms die due to insufficient oxygen.